Apparatus for forming normal stitches

ABSTRACT

A method and apparatus for forming only normal stitches between threads. Normal stitches are those usually formed by sewing machines such as lockstitch or single or double thread chain stitch machines that do not have half-hitches or extra twists between the threads. The method comprises the steps of positioning the threads in a predetermined relation to stitch forming instrumentalities and then forming a stitch. The apparatus comprises means for adjusting the relative position of the threads prior to stitch formation and means for forming stitches between the threads.

PAFENTED W 7 SHKU 1 OF 6 PATENIEDIAY 1 19m SHEEI 2 0F 6 PATENTEU HAY71974 SHEEI 3 OF 6 PATENTEDHAY 7 m4 SHEET 8 BF 6 FLyZO I APPARATUS FORFORMING NORMAL STITCHES BACKGROUND OF THE INVENTION This inventionrelates to a method and apparatus for forming only normal stitchesbetween threads.

Efforts to automate sewing machines and other stitch forminginstrumentalities have increased in recent years as the cost anddifficulty of obtaining skilled machine operators has increased. Many ofthese attempts at automating sewing operations such as that described inco-pending U.S. Pat. application Ser. No. 94,772 filed Dec. 3, 1970, inthe names of Hans F. Schaefer, Jr. and Reade Williams have includedmeans for automatically moving a workpiece in relation to stitch forminginstrumentalities. The means for moving a workpiece described in theabove application differ from those traditionally employed in sewingmachines in that the unidirectional reciprocating workpiece movingmethod or feed dogs traditionally employed are' replaced by means formoving the workpiece in multiple directions, usually along substantiallyorthogonal coordinates designated X and Y. These new moving means areappropriately controlled by automatic control means such as a numericalcontrol to cause relative motion between the workpiece and stitchforming instrumentalities along a predetermined path which may includeall vector directions relative to the instrumentalities within the planedefined by the orthogonal coordinates. In contrast, the feed dogs andmanual control traditionally employed in sewing machines producedrelative movement between a workpiece and the stitch forminginstrumentalities having vector directions within a few degrees of thedirection of motion of the feed dogs or essentially tangential to thepath being sewn.

Movement of the workpiece relative to the stitch forminginstrumentalities along a wide range of vector directions produced twounexpected problems. As the workpiece is moved relative to the stitchforming instrumentalities, the stitch last formed in the workpiece bythe instrumentalities draws thread from storage spools associated withthe instrumentalities in a direction having a vector component in thedirection in which the material has carried the last formed stitch. Thethread may thus assume a range of vector component directions as wide asthe workpiece movement. In certain of these directions, it has beenfound that the stitch forming instrumentalities then form a next stitchwith an extra twist or half-hitch. For this reason this problem iscalled half-hitching.

A second problem is created by the multidirectional movement ofworkpieces relative to common stitch forming instrumentalities. Incommon instrumentalities neither thread is coaxial with a reciprocatingneedle of the instrumentalities used to periodically pass thread throughworkpieces to form stitches. Certain directions of workpiece movementmay thus draw thread, as above described, into the path of reciprocatingneedle motion while the needle is out of the workpiece. Stitch formingmovement of theneedle through the workpiece will then intersect thethread in the path of the needle. During such intersection the needlemay cut or part the thread, resulting in an abnormal stitch. Thisproblem is thus called thread cutting.

The inventor has discovered that half-hitching results from the position'of the threads relative to the stitch forming instrumentalities justprior to forming a stitch. These positions are effected by the vectordirection in which the threads have been moved as the last formed stitchin the workpiece draws these threads in the direction of workpiecemovement. The inventor has also discovered that thread cutting alsoresults from thread position produced by workpiece movement. Both half-,

hitching and thread cutting result in abnormal stitches.

SUMMARY OF THE INVENTION Accordingly, it is an object of the inventionto provide a method and apparatus for forming only normal stitcheswithout half-hitches.

To this end, the method provides an additional step to thosetraditionally employed to form stitches. The additional step comprisespositioning the threads in a predetermined position relative to thestitch forming instrumentalities which position is known to permit thestitch forming instrumentalities to form a normal stitch. Since theposition 'of the threads prior to forming a stitch has now been found tobe affected by the vector direction of workpiece movement betweenstitches, a preferred form of the method provides adjustment of thethread positions by adjusting the vector direction of workpiece movementfrom the last formed stitch to the next formed stitch.

The apparatus for carrying out the method of the invention comprisesmeans operative on one of the threads to cause the stitch forminginstrumentalities to form only normal stitches. A preferred embodimentof the apparatus has means for adjusting the position of the threadsrelative to the stitch forming instrumentalities prior to forming astitch. In the preferred embodiment the adjustment of thread position isprovided by means for adjusting the direction of workpiece movementsince the last formed stitch was made which, in turn, adjusts theposition of the threads.

It should be clearly understood that embodiments other than thosedescribed as preferred are contemplated within the scope of theinvention. The embodiment hereinafter described to be preferred includeslockstitch forming instrumentalities. However, it is contemplated thatthe invention is applicable to other types of stitch forminginstrumentalities. For example, when the invention is employed withsingle thread chain stitch forming instrumentalities the threadsreferred to herein are actually different portions of a single thread.It should therefore by understood that it is not intended. to limit theinvention to an embodiment described.

BRIEF DESCRIPTION OF THE DRAWINGS There is hereinafter described apreferred embodiment of the invention which is intended to illustrateand not limit the invention and which is further described hereafter inrelation to the drawings, in which:

FIG. 1 is a perspective view of an automatically con trolled sewingmachine for practicing the invention;

FIG. 2 is a view of normal stitches;

FIG. 3 is a view of stitches having half-hitches;

FIGS. 4 through 7 are partial views of lockstitch forminginstrumentalities showing the progressive formation of a normal stitchwhen threads are oriented in a conventional direction;

FIGS. 8 through 11 are views similar to FIGS. 4 7 but showing theprogressive formation of an abnormal stitch when the threads are in adifferent direction;

FIGS. 12 through 15 are further progressive views showing the formationof a normal stitch when the threads arrive at the same direction asFIGS. 8 11 via a different direction;

FIGS. 16 through 19 are still further progressive views showing theformation of anabnormal stitch when the threads are in a still differentdirection; and

FIG. 20 is a partial view of the machine in FIG. 1 showing particularmeans for carrying out the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a lockstitch sewingmachine of a type long known in the art upon which the workpiece movingmeans have been replacedby motor operated means generally indicated at12 The workpiece moving means include means for moving the workpiecealong an-X axis 14 and an orthogonal Y axis 16. A control 18simultaneously and coordinately operates the moving means associatedwith each axis to' move a workpiece along a predetermined path which mayinclude any vector direction relative to the machine within the planedefined by the coordinate X and Y axes.

The X and Y axes and the workpiece moving means associated with the axesare additionally mounted on a pivot 20 secured to the machine along alongitudinal center line of a needle 22 of stitch forminginstrumentalities, generally at 24, of the machine. Thus, although theworkpiece may rotate relative to the machine, the workpiece does notrotate relative to the X and Y axes; so that a particular path ofworkpiece movement rela- V tive to the machine 10 may be accomplished bya single set of control instructions from the control 118 to the movingmeans associated with the X and Y axes irrespective of the rotationalorientation of the axes relative to the machine. The direction ofworkpiece movement relative-to the machine, however, is alteredbyrotation of the workpiece moving means 12. As used herein, the .vectordirection of workpiece movement will always refer to workpiece movementrelative to the machine 10 unless specifically recited to refer toworkpiece movement relative to the X and Y coordinate axes l4 and 16 ofthe workpiece moving means.

As seen in FIG. 4 the stitch forming instrumentalities 24 include aneedle thread 26 running along the needle from a storage spool (notshown) through an eye 28 of the needle and then along a vector direction30 of workpiece movement. The instrumentalities also include a bobbinthread 32 running below the workpiece from a bobbin (not shown) througha rotating sewing hook 34 and then along the vector direction ofworkpiece movement 30. Both threads move in the vector direction ofworkpiece movement because a last formed stitch (not shown) secures thethreads to the workpiece for movement therewith. The stitch forminginstrumentalities above described correspond to a portion of stitchforming instrumentalities well known in the art as lockstitch forminginstrumentalities.

A portion 36 of the bobbin thread 32 which emerges from the sewing hook34 is seennot to be in coaxial relation with a longitudinal center lineof the needle 22.

Such out of alignment arrangement of the thread portion 36 is typical oflockstitch forming instrumentalities because the sewing hook 34 has ahook portion 38 which rotates about the sewing hook to engage only theneedle thread as seen in FIG. 3 to form a stitch. Alignment of thebobbin thread portion 36 and the needle is thus difiicult or impossibleto accomplish. Without such alignment, the direction of workpiece andthread movement 30 will affect the position of the threads relative tothe needle. As hereafter more fully described, the direction 30 ofworkpiece movement may thus be adjusted to adjust the position of thethreads relative to e the needle to cause the stitch forminginstrumentalities to form only normal stitches. The direction ofworkpiece movement may similarly be adjusted to adjust the position ofthe threads relative to the needle to prevent the needle frompenetrating and cutting the threads.

The formation of normal. stitches shown in FIG. 2 and abnormal,half-hitched stitches shown in FIG. 3 will now be more particularlydescribed with relation to the drawings. FIGS. 4 through 7 show theformation of a normal stitch with workpiece movement 30 substantially inthe direction employed with traditional sewing machines having feeddogs, which direction is also substantially along the X axis 14. Theworkpiece 40 is preferably stationary during stitch formation havingmoved in the direction 30 between the formation of stitches but may alsocontinue to have a component of motion I in the direction 30. However,motion of the workpiece during stitch forming penetration of theworkpiece by the needle must not be such as to break the needle whilethe needle is inserted in the workpiece. During stitch formation theneedle 22 penetrates the workpiece 40 carrying with it the needle thread26 in the eye 28 of the needle. The needle thread below the workpiece isengaged by the hook 38 of the sewing hook as seen in FIG. 5 and carriedaround the sewing hook 34 by rotation of the sewing hook as seen in FIG.6. The needle. thread is drawn out of engagement with the hook 38as thehook again approaches the needle by further workpiece movement drawingthe thread in the direction 30. A normal stitch 39 is thus formed asseen in FIG. 7.

Referring now to FIGS. 8 through 11 a new direction of workpiecemovement 42 has been obtained by rotating the workpiece approximatelyclockwise of the direction 30 or slightly past the Y axis 16. The needlethread 26 has thus been carried behind the needle as seen in FIG. 8while the bobbin thread 32 is in front of the needle as seen in FIG. 8.The. needle 22'then carries the needle thread through the workpiece andinto engagement with the-hook 38 of the rotating sewing hook 34 whichcarries the thread around the sewing hook. As the needle 22 withdrawsfrom the workpiece, renewed workpiece movement in the direction 42 drawsthe thread 26 out of engagement with the hook 38 and into stitchformation. The stitch, however, has an extra twist or half-hitch 44 andis thus an abnormal stitch.

Referring now to FIGS. 12 through 15 the direction of workpiece movement42 is the same as that shown in FIG. 8 but having in FIG. 12 beenreached by rotation of the workpiece 265 counterclockwise from thedirection 30. The needle thread 26 and the bobbin thread 32 are thusboth in front of the needle as seen in FIG. 12. The needle thread iscarried through the workpiece by the needle, engaged by and carriedaround the sewing hook 34 and drawn away from the stitch 39.

Referring now to FIGS. 16 through 19 the direction of workpiece movement46 is shown to be substantially along the Y axis 16 reached by rotatingthe workpiece 270 from the direction of workpiece movement 30 along theX axis 14. The needle. thread 26 is thus in front of the needle 22 whilethe bobbin thread 32 is behind the needle as seen in FIG. 16. The hook38 of the sewing hook engages the thread 26 and carries it around therotating sewing hook 34 until the thread 26 is drawn out of engagementwith the hook 38 by renewed workpiece movement in the direction 46. Astitch 44 having an extra twist or half-hitch is again formed in thethreads.

As illustrated in FIGS. 4 through 19, the formation of normal orabnormal stitches is dependent upon the orientation of the sewingthreads relative to the needle 22, particularly, the threads must be ona common side of the needle. Thread cutting is similarly dependent.Thus, orientation of the threads on opposite sides of the needleresulting in formation of abnormal stitches is seen to be dependent uponcertain direction of workpiece movement and the rotation of theworkpiece undertaken to achieve that direction of movement, hereafterreferred to as forbidden directions.

The apparatus for carrying out the method of the invention is thusprovided withmeans generally at 48 to 1 rotate the workpiece out of theforbidden directions.

The means comprise a pivot 20 rotatably supporting the conventional X Yworkpiece moving means 12. A cylinder 51 is secured to a frame ofmachine and a piston rod 42 of the cylinder is connected through pivot54 to an arm 56 of a sleeve 53 on pivot and secured to the workpiecemoving means 12. Actuation of the cylinder 51 is thus effective torotate the workpiece moving means 12 about pivot 20. The extent ofmovement of the piston relative to the cylinder to produce rotation ofthe workpiece moving means sufficient to orient both threads on the sameside of the needle is determined by the particular construction of thesewing machine 10 employed. However, the workpiece moving means 12 mustrotate a number of degrees at least equal to the maximum number ofconsecutive degrees constituting a zone of forbidden directions. In thisway actuation of the cylinder will always rotate the workpiece movingmeans out of a zone of forbidden directions. In a-preferred embodimentof the invention the control 18 provides means (not shown) forautomatically actuating the piston and cylinder. However, in anotherembodiment a manually operated switch may be provided for this purpose.

In correspondence with the apparatus, a preferred form of the method ofthe invention comprises adjusting the position of the threads prior toforming stitches to permit stitch forming instrumentalities to form onlynormal stitches. The adjustment may be accomplished by rotating thedirection of workpiece movement out of a zone of forbidden directions.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent of the United States is:

1. A stitching machine comprising:

A. an automatically controlled support for moving a workpiece inrelation to stitching instruments, said support being capable of movingsaid workpiece in directions in which abnormal stitching will occur; and

B. means operatively connected to the automatically controlled supportto move the workpiece away from directions of abnormal stitching.

2. A stitching machine as described in claim .1 wherein theautomatically controlled support is pivotally mounted on the stitchingmachine and the means are operative on said support to cause pivotalmovement thereof.

3. A stitching machine comprising:

A. an automatically controlled support for moving a workpiece inrelation to stitching instruments pivotally mounted on the stitchingmachine, said support being capable of moving said workpiece indirections in which abnormal stitching will occur;

B. piston and cylinder means operatively connected to the automaticallycontrolled support to pivot the workpiece away from the directions ofabnormal stitching; and

C. switching means operative to energize the piston and cylinder meanswhen directions of abnormal stitching are called for by the automaticcontrol.

1. A stitching machine comprising: A. an automatically controlledsupport for moving a workpiece in relation to stitching instruments,said support being capable of moving said workpiece in directions inwhich abnormal stitching will occur; and B. means operatively connectedto the automatically controlled support to move the workpiece away fromdirections of abnormal stitching.
 2. A stitching machine as described inclaim 1 wherein the automatically controlled support is pivotallymounted on the stitching machine and the means are operative on saidsupport to cause pivotal movement thereof.
 3. A stitching machinecomprising: A. an automatically controlled support for moving aworkpiece in relation to stitching instruments pivotally mounted on thestitching machine, said support being capable of moving said workpiecein directions in which abnormal stitching will occur; B. piston andcylinder means operatively connected to the automatically controlledsupport to pivot the workpiece away from the directions of abnormalstitching; and C. switching means operative to energize the piston andcylinder means when directions of abnormal stitching are called for bythe automatic control.